(1) Field of Invention
This invention relates to a device and a method for controlling motor operation.
(2) Background Art
In order to conduct recording with a printer wherein a carriage runs across a recording medium, it is necessary to accelerate the carriage up to specific speed, and after moving the carriage across a section above the recording medium at the specific speed, the carriage needs to be promptly decelerated so as to stop at a predetermined target stop position, that is a position wherein minimum acceleration distance for return movement is maintained. Alternatively, the carriage needs to be decelerated so as to stop at a position located slightly further than the target stop position and besides a nearest possible position to an onset of a permissible section for stoppage.
Simply by reducing rotational speed of a motor that drives the carriage after the carriage enters a deceleration section, the traveling speed of the carriage may not be sufficiently lowered due to inertia. For this reason, combinations of braking methods, such as regenerative braking, reverse rotation braking (plugging) and short-circuit braking, have been conventionally used to stop a carriage at a target stop position or at a nearest possible position to an onset of a permissible section for stoppage, that is slightly further than the target stop position.
In the case where the traveling speed of the carriage is reduced by this braking method, the traveling speed of the carriage may be reduced more than necessary due to braking effect, and the carriage may stop before reaching the target stop position (that is, the carriage may undershoot). Nevertheless, a motor is controlled in a manner so that the carriage initiates moving again from the position where the carriage has stopped, and the carriage eventually reaches the target stop position. In respect of the movement of the carriage, there is no problem with this operation. However, time required for the carriage to reach the target stop position becomes long, since the carriage stops once and then initiates the movement again.
In order to solve this problem, Japanese Unexamined Publication No. 57-43888 discloses a technique wherein the traveling speed of the carriage is once reduced from a normal traveling speed (a steady speed v1) to a constant speed (a low speed v2) by braking the carriage, when the carriage (carrier) enters a deceleration section. After moving the carriage for a predetermined distance (up to a predetermined position P) at the reduced speed (v2), braking is again conducted to reliably stop the plant (carrier).